A day without pay, the first of 11 through September, comes next week for more than 650,000 people who hold civilian jobs with the Defense Department. Officials worry that the Pentagon will be hit even harder by layoffs in 2014 if automatic budget cuts continue as planned.

The Afghan war effort eventually would be harmed by across-the-board budget cuts, even as the Obama administration intends to shield the military’s combat mission from the reductions, the Pentagon’s No. 2 official said Friday.